The invention relates to an X-ray tube comprising an anode and a cathode which are accommodated in an envelope comprising a high-voltage connection and an exit window.
An X-ray tube of this kind is known from EP 168.641. An X-ray tube described therein comprises a cathode provided with a filament in the form of a flat helix and also comprises a conical anode whose cone axis extends transversely of the center of the helical filament. In order to avoid excessively high temperatures in a central part of the anode, the temperature of an oppositely situated part of the filament is adjusted to a value which is lower than the temperature of the peripheral part of the helix. Even though the central anode temperature can be reduced by means of such a construction, it has been found that for many applications or anode constructions this solution is inadequate to ensure a comparatively long service life of the X-ray tube.